Photographic methods in which silver halides are used have been widely used in the past since they provide better photographic characteristics, such as photographic speed and gradation control, than do other photographic methods such as electrophotography or diazo photography. Color diffusion transfer processes in which a photosensitive element which has a silver halide emulsion layer and an image receiving element which has an image receiving layer are superimposed on one another and an alkaline processing composition is spread in the form of a layer inside the combination, or the combination is immersed in an alkali processing bath, are included among photographic methods in which silver halides are used. In recent years, techniques from which images can be obtained easily and quickly by the application of a dry process with heating, for example, have been developed apart from the wet methods using conventional development baths for the formation of an image with photosensitive materials in which silver halides are used.
Methods of image formation with thermal development have been disclosed, for example, in JP-A-57-179840, JP-A-57-186774, JP-A-57-198458, JP-A-57-207250, JP-A-58-58543, JP-A-58-79247, JP-A-58-116537, JP-A-58-149046, JP-A-59-48764, JP-A-59-65839, JP-A-59-71046, JP-A-59-87450, JP-A-59-88730, JP-A-62-253159 and European Patent 220,746A2. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".)
These are methods in which mobile dyes are formed or released in proportion, or in inverse proportion, to the reaction when a photosensitive silver halide and/or organic silver salt is reduced by heat development to silver, and the mobile dye is transferred to a dye fixing element.
The method of forming images by transferring a diffusible dye formed by heat development to an image fixing element has a major advantage in that the dye image can be obtained easily and quickly. However, when the image obtained is stored for a prolonged period of time, the colors are liable to fade or change for reasons different from those seen in color images formed by the ordinary wet processing. This is because heat is applied during the image formation or transfer and, therefore, the dyes cause denaturation by themselves, or substances which impart adverse influences with respect to color fading or change are formed and transferred to the dye fixing element together with the dyes.